SAND, GRAVEL AND CRUSHED STONE AVAILABLE FOR 

 CONCRETE CONSTRUCTION IN MANILA. 



By Geoege I. Adams. 

 {From the Division of Mines, Bureau of Science.' 



Wi\\\& making a geological reconnaissance of southwestern Luzon, 

 special attention was paid to the occurrence and availability of structural 

 materials. In this area which produces no metallic minerals, the value 

 of the stone, gravel, sand and clay products used during the. last year 

 surjDassed that produced by any mining district in the Islands. Most 

 of this output was used in and near Manila. 



It is a surprising fact that sand and gravel taken from the Pasig and 

 Mariquina Eivers have sold at the dredges for more per cubic meter 

 than the average value of the gold per meter in good gold-dredging 

 ground, and that the price of crushed stone at the quarries has in some 

 cases been so high as to make the quarrying compare favorably, consider- 

 ing the expenses of production, with the mining of low-grade ores. 

 The problem of the cost of structural materials in Manila should resolve 

 itself without any special investigation. It is the purpose of this report 

 to discuss the nature of the materials which are commonly used, to show 

 where other and better ones may be obtained, and to indicate their 

 relative eflSciencies in concrete construction. 



SAND. 



Sources. — Most of the sand used in Manila is dredged from the Pasig 

 Eiver or dipped up in baskets and loaded into baneas by native divers. 

 Some is also obtained from the Mariquina Eiver which enters the Pasig 

 just below the town of Pasig. The Pasig is the outlet of Laguna de 

 Bay and does not bring coarse sediments from the lake. Accordingl}-, 

 such sands and gravels as are found in its bed are received almost entirely 

 from the Mariquina, which is its principal tributary, and the only large 

 stream from the Eastern Cordillera which Ijrings erosional products to 

 the vicinity of Manila. (See fig. 1.) 



463 



